Last spring, researchers confirmed that brown fat—the kind that burns energy rather than storing it and is especially prevalent in newborns—can be found in small pockets in adults, too, and slimmer adults have more of it. This spring, a team says it might have found one of the first steps in activating that fat-burning fat in adults. Their study comes out in Science this week.
Brown fat is packed with energy-producing mitochondria, and babies have a lot of it because it helps them keep warm. Once humans begin to regulate their own body temperature they don’t need as much brown fat anymore, so it gets replaced by energy-storing white fat, which helps store energy but leads to expanded waistlines in this age of affluence.
Testing on mice, the team led by Stephan Herzig upped the use of an enzyme called cyclooxygenase-2 (COX-2). While the enzyme plays a role in many physiological functions, the researchers found that pushing it in mice could induce their white fat to act more like energy-burning brown fat, and their weight dropped by around 20 percent.
“There has been a lot of excitement around brown fat, but … there wasn’t any clear indication that turning up brown fat would make animals lose weight,” says Chad Cowan, a professor in the Department of Stem Cell and Regenerative Biology at Harvard Medical School who studies fat cell development. “What this paper does is make a good link to something that might be clinically beneficial [TIME].
From the skin cells of humans and mice, scientists have successfully made brown fat, the kind that burns white fat by producing heat and is possessed in the greatest quantities by babies. The study, published in Nature, could potentially lead to a way to help overweight and obese people slim down.
Brown fat was once thought to be found only in children, but earlier this year researchers confirmed that adults also have a small amount of brown adipose tissue. In 2007, researchers discovered that a protein called PRDM16 made immature muscle cells turn into brown fat. In the new Nature study, the same team of scientists found that PRDM16, in combination with a second protein produced in muscle cells, is the master switch for brown fat cells and will also convert skin cells into brown fat, even though this is not the process nature intended. [Scientists] used this master switch to convert mouse skin cells to brown fat cells, which seem to work as expected when transplanted into normal mice [The New York Times]. The next step is to implant brown fat into obese mice to see if they lose weight; that will provide evidence that the discovery might be used outside of the lab.